1. Field of Invention
The field of the currently claimed embodiments of this invention relates to—electro-optic devices and methods of production, and more particularly to organic electro-optic devices.
2. Discussion of Related Art
Solar cell technology has been expected to be the most effective method for producing clean energy at low cost and minimum pollution. Beginning from the last century, solar cell technologies have evolved based on various material systems used for harvesting the solar energy. The most traditional, yet the most commonly available kind of solar cell technology is based on the utilization of crystalline silicon as the active absorbing material. However, due to the high cost of purifying silicon into high crystalline state, the application of silicon-based solar cells as a major energy source is limited.
In recent years, conductive and semi-conductive conjugated polymers have attracted much attention for their applications in organic photovoltaics (OPVs) and organic light emitting diodes (OLED). Organic photovoltaics have drawn intense attention due to their advantages over competing solar cell technologies. Current progress in the power-conversion efficiency (PCE) of OPVs has overcome the 10% PCE barrier, suggesting a promising future for OPVs as a low-cost and highly efficient photovoltaic (PV) candidate for solar energy harvesting. In addition to the pursuit of high device efficiency, OPVs are also intensely investigated for their potential in making advances in much broader applications. One of these applications is to achieve high-performance visually transparent or semi-transparent PV devices, which could open up PV applications in many untapped areas such as building-integrated photovoltaics (BIPV). The advantages of OPVs, such as low cost, ease of processing, flexibility, lightweight and highly transparent, make polymer solar cells (PSCs) a good candidate for BIPV purpose.
Previously, many attempts have been made to demonstrate visually transparent or semi-transparent OPV cells (TOPV or s-TOPV). We define TOPVs as organic solar cells that have an average transparency within the visible light region (400 nm˜650 nm) (Tave-vis) of ≧50% and s-TOPVs as organic solar cells that have Tave-vis between 0% and 50%. Transparent conductors, such as thin metal films, metallic grids, metal nanowire networks, metal oxide, conducting polymers, and graphene, have been deposited onto OPV active layers as back electrodes to achieve a solution-processable TOPV or s-TOPV. However, due to the absence of efficient solution processable transparent conductors and effective device architectures, these demonstrations often result in low device performance. Therefore, there remains a need for improved organic electro-optic devices.